The invention disclosed herein represents an improvement over that shown and described in a prior co-pending application entitled "Control System For Glassware Machine" in the names of Mylchreest and Wythe filed June 29, 1973 under Ser. No. 374,818.
As disclosed in the above mentioned patent application the normal cycle of a typical individual section glassware forming machine can be rendered more versatile by dividing its cycle up into modes related to the thermodynamics of the dynamic glassware forming process. More particularly, these modes are defined by boundary event timings which can be related to certain key mechanical functions, and a computer is disclosed for use in controlling certain other machine functions within a particular mode. These boundary event timings not only control other event timings within a particular mode, but are variable within predetermined limits. However, the above mentioned patent application suggests use of a pulse generator to trigger a counter to develop discrete counts for use by a comparator wherein these counts are compared to desired values stored in memory. An output from this comparison operates a solenoid controlled valve block which is analagous to the mechanically actuated valve block in the conventional pneumatically operated type of glassware machine.
As disclosed in the present application a shaft encoding device is adapted to provide a voltage signal indicative of the angular position of a shaft associated with the mechanical drive for the feeder itself, and this shaft encoder signal is converted to binary coded decimal (BCD) form in order to permit use of a digital computer for carrying out the comparison concept disclosed in the above mentioned co-pending patent application. As a result of the improved system disclosed herein the need for a counter is obviated.
Among the prior art approaches to adapting the typical Hartford I. S. type of glassware forming machine to electronic control is the system disclosed in U.S. Pat. No. 3,762,907 issued to Quinn et al Oct. 2, 1973. This prior art patent provides a pulse generator for producing a series of pulses proportional in frequency to the rotational speed of the take-away conveyor drive shaft. A master counter, and associated gate circuitry, provide timed signals to the various machine sections. Still further counter circuitry is associated with each of the individual machine sections for actually operating the glassware forming mechanisms. This additional circuitry includes individual section counter means and associated switch gating to permit sequential operation of solenoid valves associated with the various mechanisms of each of the individual machine sections. A major disadvantage incident to the adoption of this disclosure in the environment of a typical glassware forming machine resides in the considerable expense involved in providing hard-wire electronic circuitry for the control of each of the various sections in a typical six or eight section Hartford I. S. type of machine. The present invention adopts a digital computer in the control system to be described herein, eliminating much of the complex electronic circuitry provided in this prior art disclosure, and as a consequence of the versatility inherent in such digital computers, the present invention has the additional advantage of permitting changes to the timing of the various mechanical mechanisms under the supervisory control of a program stored in such digital computer.
The advantages of the present invention can best be delineated by reference to the conventional cycle of operation of the Hartford I. S. machine. However, the description to follow defines this cycle by reference to certain boundaries which relate the thermodynamics of the glassware forming process to the mechanical machine functions normally provided in the conventional machine. These boundaries permit the use of a computer or controller to be so programmed that the machine operator can manually alter these boundaries by predetermined increments to vary machine operation and to improve the machine's efficiency at the press of button, the related machine functions being automatically revised as required in accordance with the program, and the selected change being automatically cancelled if any of these functions will be outside of predetermined limits.
In a typical Hartford I. S. type of glassware forming machine, molten glass gobs are delivered, by means of a gob distribution system, in a predetermined sequency to the upwardly open blank .Iadd.molds .Iaddend.of the various machine sections. Each section comprises a self-contained unit which includes a blank mold station and a blow mold station. The gob of molten glass is formed into a parison at the blank station, and then transferred to the blow station by a neck ring arm which includes a neck mold. The neck mold not only mates with the blank mold at the blank station but also serves to support the parison during transfer to the blow station.
The blank mold may be of the split or the solid type but in the description to follow a two part split blank mold is provided, and is adapted to mate with the neck mold. The neck mold is also of the split type, and is annular in shape with a central opening to receive a vertically reciprocable plunger which presses the gob upwardly into the blank mold in the "press and blow" process, or which plunger is associated with a thimble to permit the parison to be formed by the "blow and blow" process. This latter process provides for "counter blow" air at the blank station in addition to the "final blow" air at the blow station. The description to follow contemplates forming glassware by a blow and blow process, but could also be adapted for use in the press and blow process.
The glass gobs are formed at rate determined by the machine operator, and these gobs are fed through a distribution system to the various blank mold cavities. Each blank cavity is upwardly open, and a funnel is usually provided to move in onto the closed blank mold for guiding the gob into such cavity. The gob drops through the funnel, into the cavity, and into the neck mold, which is always closed except for a short time at the blow station for release of the parison. In this "delivery mode" of the machine the plunger and the thimble must be raised to define the neck opening of the ware. This initial mode is synchronized with the gob distributor system.
The next mode of operation of the machine can be characterized as one of "settling" the gob or charge into the neck mold to form the finish of the ware. This is accomplished in the usual blow and blow process by bringing a baffle down onto the funnel, and providing air to the baffle for settling the charge in the blank mold. If no funnel is used in loading the gob, the baffle may move directly in on top of the blank mold. As so configured the blank station of the machine section is in its "parison settle" mode. After settle blowing has been completed the baffle, and funnel, are returned to their inactive positions, respectively.
The next mode of operation of the machine occupies only a short time, and can be characterized as "parison corkage reheat". The plunger moves downwardly away from the neck of the parison allowing the heat of the glass to stabilze in this part of the parison. This short pause softens the inside glass surface by internal conduction, at least in the area where the plunger tip has caused it to cool during the "delivery" and settle modes, and as so configured the machine is in its "corkage reheat" mode.
The next mode of operation of the machine can be characterized as one of parison forming, and in the blow and blow process such forming is carried out by increasing counter blow air to the softened area of the parison. The mechanical machine configuration is only altered from the previous mode in that the baffle is lowered onto the blank mold. This mode will see the gob expanded to fill the upper regions of the blank cavity defined by the blank mold and by the baffle. After allowing time for this preliminary forming the counter blow air is turned off, the baffle is returned to its inactive position, and the split blank mold is ready for opening. As so configured the blank station of the machine is still in its parison forming or counter blow mode.
The next mode involves reheating the parison and the initial phase is accomplished simply by opening the split blank mold. With the blank mold open the parison is not in contact with any mold parts except the neck mold. This configuration allows the heat stored in the thick walled parison to raise the temperature of its surfaces, hence the derivation of the term reheat mode. This phase can be called blank side reheat.
After the blank mold has completely opened, the neck ring arm inverts the neck mold and the parison along with it. This phase of the reheat mode can be characterized, thermodynamically, as "invert reheat". As the parison reaches the blow station the third phase of reheat starts as "low side reheat". The blow mold closes around the parison and around a bottom plate, which will be spaced below that end of the parison opposite its neck or open end. The blow mold has an upper portion which supports the parison from just below its finish, allowing the neck mold to be opened prior to revert, or return movement of the neck ring mold. The neck ring mold recloses during return movement so that the blank mold can close around it once the neck mold has returned to the blank station.
The next mode involves final forming of the body of the ware, the finish of the ware having been formed by the neck mold at the blank station. The final blow air is delivered to the interior of the parison by a blow head which moves down onto the top of the closed blow mold. After a preset time for final blowing the air is turned off and the blow head returned to its inactive position. At the end of the final blow mode, the blow mold opens and take-out tongs (open) are swung into the blow station starting the take-out mode. The tongs close around the newly formed ware and the article is lifted off the bottom plate for delivery to the deadplate portion of a take-away conveyor system.
The concept of dividing the cycle of operation of a glassware forming machine into various modes associated with a particular section, as referred to above, is shown and described in the above mentioned co-pending patent application. However, in said co-pending patent application, counter means is required as an adjunct to the use of a pulse generator in order to provide the requisit control of the various mechanical mechanisms or means associated with each machine section. As disclosed therein a pulse generator is used to trigger counter means, which develops counts for use by gate or comparator circuitry in order to produce an output signal suitable for operating a solenoid controlled valve block. Although the prior co-pending application discloses two types of channels for handling the information, one channel comprising a boundary channel and the other type of channel comprising a preset count determined by the boundary channel value, it will be apparent from the description to follow that the present disclosure relates to a control system for a glassware .Iadd.forming .Iaddend.machine which permits use of a digital computer with a memory and associated program storage in place of the counter and gating circuitry characteristic of prior art approaches especially as disclosed in the prior co-pending application mentioned herein, and in the Quinn et al. Pat. No. 3,762,907.